nado, good afternoon.
(1) What a great question! Even native speakers occasionally get confused.
(2) "Historical" just means part of history. So everything is historical.
(3) "Historic" means something part of history that is SPECIAL.
(a) In my city, for example, the government has decided that a few old houses are historic. That is, maybe a famous person lived there; maybe it was built in the 19th century. The city will not let anyone demolish (destroy) them.
(b) I hear that many parts of Cairo are historic. That is, very old. Very special. *** The Great Wall of China is historic. *** The Colosseum in Rome is historic.
(4) It is very nice that you want to use these two words correctly.
Have a nice day!